1. Field of the Invention
The present invention relates to an apparatus for alignment processing which irradiates a moving substrate with polarized light via a plurality of photomasks to form two types of alignment regions having different alignment states of liquid crystal molecules that are alternately arranged into a stripe form, and more specifically, relates to an apparatus and a method for alignment processing which reduces alignment disturbance of liquid crystal molecules formed along a stitching line between a plurality of photomasks.
2. Description of Related Art
Conventionally, this sort of an apparatus for alignment processing is one which employs a photomask having a plurality of first and second apertures arranged alternately in parallel at a constant pitch so that two polarized lights having different incident angles, pass through the respective apertures, and the apparatus is configured to irradiate a substrate, that is being scanned under the photomask, with the two polarized lights through the photomask to form first and second alignment regions having different alignment states of liquid crystal molecules adjacent to each other on an alignment film coating the substrate (see, for example, refer to Japanese Laid-Open Patent Application No. 2010-39485).
In such a conventional apparatus for alignment processing, in order to apply alignment processing to a large-area substrate in a single step, as illustrated in FIG. 10, it is necessary to arrange a plurality of photomasks 2 alternately in a direction intersecting a scanning direction of the substrate so that the plurality of the first and the second apertures 1A and 1B are arranged in the direction intersecting the scanning direction of the substrate (indicated by an arrow A) at a constant pitch P, and furthermore, it is necessary to move the photomasks 2 so as to follow a movement of the substrate in the direction intersecting the scanning direction of the substrate that is scanned under the photomask 2. In this case, since the first and the second apertures 1A and 1B can be formed by using a photolithography technique, it is possible to form these apertures with high positioning accuracy in the photomask 2. Accordingly, in general, as illustrated in FIG. 10, the apertures 1A and 1B in the same photomask 2 are each formed to have a width W in the direction intersecting the substrate-scanning direction that is equal (W=P) to their arrangement pitch P in the direction so that ends of first and second alignment regions 3A and 3B parallel to the substrate-scanning direction indicated by an arrow A (refer to FIG. 11) contact with each other.
However, when an alignment process is carried out by employing a plurality of such photomasks 2, as illustrated in FIG. 11, a multiple-exposure region 4 having a width corresponding to an tracking accuracy (±Δw) of the photomask 2 to the substrate 2 is formed along a stitching line between a plurality of photomasks 2, thus disturbing alignment in the region. Accordingly, if an alignment-processed substrate 9 having such a multiple exposure region 4 is employed, for example, in a display device, a streak, that is a bright line or a dark line corresponding to the multiple-exposure region 4, may be formed in a display screen. Particularly, when such a streak is formed in a part of the display screen, there occurs a problem that the streak is recognized as a defect since human eyes are sensitive to such a streak.
Under these circumstances, it is an object of the present invention to address the problems and to provide an apparatus and a method for alignment processing which reduce visibility of disturbance of alignment of liquid crystal molecules formed along a stitching line between a plurality of photomasks.